336 SCIENCE PROGRESS 



possible methods will feel to be rather, weak. To give three examples out of 

 perhaps a dozen : no reference is made to any simple difference method for 

 measuring time periods, the student is only told to determine the time taken for 

 fifty swings ; again, in the calibration of a thermometer it is never desirable to 

 detach a mercury thread by applying a flame — a suitable length can always be 

 obtained quite safely from ordinary thermometers by jerking them ; finally, in the 

 magnetometry no hint is given as to the limits within which the approximate cube 

 law of magnetic force may be applied, and there is no mention at all of the more 

 accurate calculation which can be made if the deflections are taken at two 

 distances instead of one. 



Hardly sufficient stress has been laid on the accuracy needed for the in- 

 dividual measurements in an experiment in order to obtain the best possible 

 result. The beginner never thinks of this for himself, and it should be brought 

 to his notice whenever possible. A notable opportunity occurs in calorimetry, 

 where the accuracy of the final result is usually limited by that with which the 

 small rise of temperature in the calorimeter can be determined. In spite of this 

 the specimen data quoted as an example of a latent heat of fusion of ice experi- 

 ment on p. 351 are as follows : — Masses of calorimeter, etc., 40 gm., 240 gm., and 

 262*9 & m - Temperatures 10° C. and 20 C. Such figures would call for a good 

 deal of red ink if presented in a laboratory note-book ! And even intermediate 

 students should be provided with a thermometer divided into tenths for measuring 

 the calorimeter temperatures. 



Space does not permit of a detailed criticism of the separate parts, but a few 

 words of praise must be given to the section on current electricity which occupies 

 a quarter of the whole book. It is not overloaded with a great number of un- 

 important experiments, representing all the freakish combinations likely to be 

 devised by an examiner out for "something different" at all costs ; while on the 

 other hand it does contain every important one described with painstaking care 

 and clearness. Many descriptions are followed by notes, as, for example, con- 

 cerning the conditions under which the method may be employed with advantage. 

 This information is generally left to be imparted by the demonstrator ; it is only 

 too often forgotten at once and ought to be given permanent record in the text- 

 book. A few simple experiments with dynamos and motors are included for those 

 proceeding to a course on electrical engineering, and the section closes with 

 a very excellent collection of notes on electrical apparatus. 



The book contains a collection of useful data, a selection from Castle's 

 Mathematical Tables and an adequate index. The line diagrams and printing 

 are all that could be desired, but the binding is rather light, and the paper seems 

 a little soft to stand the hard wear that such a book is destined to meet with. 



D. Orson Wood. 



CHEMISTRY 



Chemistry in the Service of Man. By Alexander Findlay, M.A., D.Sc, 

 F.I.C. [Pp. xiv + 255, with three portraits and 23 diagrams in the text.] 

 (London : Longmans, Green & Co., 1916. Price 5^. net.) 



It will be the task of some cynical historian of the future to point out that it needed 

 the greatest and most devastating war the world has ever seen to force the British 

 Empire to acknowledge the existence and uses of the Sciences on which its 

 welfare and security ultimately depended. The publication of the present work 

 is, however, a sure symptom of that national awakening to the manner in which 



